Method and Apparatus for Calculating Kink Current of SOI Device

ABSTRACT

The present application discloses a method and apparatus for calculating the kink current of SOI device, which is used to solve the problem that the kink current calculation in the prior art is not accurate and is not suitable for circuit simulation. The method includes: obtaining the impact ionization factor, the parasitic transistor effect factor, and the drain saturation current of the SOI device respectively; and calculating the kink current of the SOI device according to the impact ionization factor, the parasitic transistor effect factor, and the drain saturation current.

TECHNICAL FIELD

The application relates to the technical field of semiconductor devices,and in particular, to a method and apparatus for calculating kinkcurrent of an SOI device.

BACKGROUND

Silicon on Insulator (SOI) refers to the structure of a silicontransistor on an insulator substrate. SOI devices are similar to MOSFETsin structure and belong to the field effect devices, but SOI devices arefabricated on insulating substrate rather than MOSFETs on asemiconductor substrate. Broadly speaking, “Silicon” represents thechannel layer of an SOI device, and it can be not onlysingle-crystalline silicon, but also amorphous silicon, polysilicon,oxide semiconductors, organic semiconductors, etc.; “Insulator”represents the insulating layer substrate of an SOI device. It can beglass, quartz, or a silicon substrate covering a thin SiO₂ layer. Whenthe drain terminal of an SOI device is biased to a sufficiently largevoltage, its output characteristics of the SOI device will experience ananomalous current increase, namely the kink effect. The excess currentin this part is referred to as the kink current, as shown in FIG. 1. Anaccurate, analytical and physical-based kink current model is essentialfor circuit design and simulation.

The kink current calculation method for an SOI device in the prior artincludes:

{circle around (1)} Based on the floating body effect, all possiblecurrent components through the back channel are taken into account, butthe model involves many parameters and the current form is toocomplicated to be suitable for circuit simulation.

{circle around (2)} Models are introduced by calculating themultiplication factor M, such as the RPI model. In the work of Jacunskiet al., the multiplication factor M is obtained by integrating theimpact ionization rate in the drain depletion region along the depletionregion. The relationship between the kink current and the multiplicationfactor M is:

I _(kink) =M·I _(Dsat),

where I_(Dsat) is the drain saturation current and M is themultiplication factor.

The multiplication factor M can be expressed empirically as follows:

$M = {\left( \frac{L_{kink}}{L} \right)^{m_{kink}}\left( \frac{V_{D} - {\alpha_{sat}V_{GT}}}{V_{kink}} \right){\exp\left( \frac{- V_{kink}}{V_{D} - {\alpha_{sat}V_{GT}}} \right)}}$

where L_(kink) and m_(kink) are fitting parameters, L is the channellength, V_(D) is the drain voltage, V_(kink) is the drain voltage whenthe kink effect occurs, V_(GT)=V_(GS)−V_(T) is the effective gatevoltage (V_(GS) is the gate voltage, V_(T) is the threshold voltage),and α_(sat) is a parameter related to pinch-off at the drain.

The multiplication factor M in method {circle around (2)} depends on theempirical formula. It cannot be well applied to the outputcharacteristic curves at multiple gate voltages. As shown in FIG. 2, theexperimental object is a P-type polysilicon thin film transistor. Thefive output characteristic curves from bottom to top correspond to thegate voltage V_(gs)=−2,−4,−6,−8,−10V, respectively. The applicant foundthe same disadvantage when using this model for fitting. As shown inFIG. 3, the experimental object is a P-type polysilicon thin filmtransistor. The four output characteristic curves from bottom to topcorrespond to the gate voltage V_(gs)=−3.5,−4,−4.5,−5V, respectively.

Therefore, how to accurately model and calculate the kink current of SOIdevice is still a problem that needs to be solved at present.

SUMMARY

Embodiments of the disclosure provide a kink current calculation methodand apparatus for an SOI device, which are used to solve the problemthat the kink current calculation method of an SOI device in the priorart cannot be well described quantitatively.

In one embodiment, the method comprises: obtaining the impact ionizationfactor, the parasitic bipolar junction transistor effect factor, and thedrain saturation current of the SOI device respectively; calculating thekink current of the SOI device according to the impact ionizationfactor, the parasitic transistor effect factor, and the drain saturationcurrent.

In one embodiment, obtaining the parasitic transistor effect factor ofthe SOI device specifically includes:

Obtaining the channel length and the carrier diffusion length in thebody region of the SOI device, and calculating the parasitic transistoreffect factor of the SOI device according to the channel length and thecarrier diffusion length in the body region.

In one embodiment, the parasitic transistor effect factor of the SOIdevice has a hyperbolic secant dependence on the channel length and thecarrier diffusion length in the body region of the SOI device;

preferably, the parasitic transistor effect factor is:

${sech}\left( \frac{L}{L_{b}} \right)$

where L is the channel length of the SOI device and L_(b) is the carrierdiffusion length in the body region of the SOI device.

In one embodiment, the impact ionization factor of the SOI device has anexponential relationship with the threshold field F, characterizing theimpact ionization, the depletion region width I_(d), the drain voltageV_(D), and the interpolation function V_(Dse) related to drainsaturation voltage of the SOI device;

preferably, the impact ionization factor is:

${\frac{\left( {V_{D} - V_{Dse}} \right)}{l_{d}}{\exp\left( {- \frac{F_{I}l_{d}}{V_{D} - V_{Dse}}} \right)}};$

alternatively, the impact ionization factor of the SOI device has anexponential relationship with the drain voltage V_(D), the voltageparameter V_(k) associated with the kink effect, and the interpolationfunction V_(Dse) related to drain saturation voltage of the SOI device;

preferably, the impact ionization factor is:

${\frac{\left( {V_{D} - V_{Dse}} \right)}{V_{k}}{\exp\left( {- \frac{V_{k}}{V_{D} - V_{Dse}}} \right)}}.$

In one embodiment, the calculation method for kink current I_(kink) ofthe SOI device is:

$\begin{matrix}{{I_{kink} = {C\frac{\left( {V_{D} - V_{Dse}} \right)}{l_{d}}{\exp\left( {- \frac{F_{I}l_{d}}{V_{D} - V_{Dse}}} \right)}sec{h\left( \frac{L}{L_{b}} \right)}I_{Dsat}}};} & (1)\end{matrix}$

where C is a parameter related to the material and geometry of the SOIdevice, L is the channel length of the SOI device, V_(D) is the drainvoltage of the SOI device, V_(Dse) is the interpolation function relatedto the drain saturation voltage, F_(I) is the threshold field for impactionization of the SOI device, L_(b) is the carrier diffusion length inthe body region of the SOI device, and I_(Dsat) is the drain saturationcurrent of the SOI device; Or,

The calculation method for kink current I_(kink) of the SOI device is:

$\begin{matrix}{{I_{kink} = {C_{k}\frac{\left( {V_{D} - V_{Dse}} \right)}{V_{k}}{\exp\left( {- \frac{V_{k}}{V_{D} - V_{Dse}}} \right)}sec{h\left( \frac{L}{L_{b}} \right)}I_{Dsat}}};} & (2)\end{matrix}$

where C_(k) is a parameter related to the material and geometry of theSOI device, L is the channel length of the SOI device, V_(D) is thedrain voltage of the SOI device, V_(Dse) is the interpolation functionrelated to the drain saturation voltage, V_(k) is the voltage parameterassociated with the kink effect, L_(b) is the carrier diffusion lengthin the body region of the SOI device, and I_(Dsat) is the drainsaturation current of the SOI device.

In one embodiment, the method further comprises:

parameter extraction of threshold field F_(I):

obtaining drain current I_(D) and drain saturation current I_(Dsat) ofmultiple long-channel SOI devices with fixed channel width but variedchannel lengths at multiple gate voltages;

using equation (1) to establish the function with the threshold fieldF_(I) as the slope in long-channel SOI devices;

according to the drain current I_(D) and drain saturation currentI_(Dsat) of the multiple long-channel SOI devices at multiple gatevoltages, and the function with the threshold field F_(I) as the slopein long-channel devices, calculating the threshold fields for impactionization of the multiple long-channel SOI devices at multiple gatevoltages; preferably,

the method further comprises:

parameter extraction of carrier diffusion length L_(b) in the bodyregion:

using equation (1) to establish the function with

$- \frac{1}{L_{b}}$

as the slope in long-channel SOI devices;

calculating the average value of the threshold fields for impactionization of each long-channel SOI device at multiple gate voltages,respectively;

according to the average value of the threshold fields for impactionization of each long-channel SOI device at multiple gate voltages,and the function with

$- \frac{1}{L_{b}}$

as the slope in long-channel devices, calculating the carrier diffusionlengths in the body region of the multiple long-channel SOI devices atmultiple gate voltages; preferably,

the method further comprises:

extraction of parameter C:

calculating the average value of carrier diffusion lengths in the bodyregion of the multiple long-channel SOI devices at multiple gatevoltages:

according to the average value of carrier diffusion lengths in the bodyregion of the multiple long-channel SOI devices at multiple gatevoltages, and the average value of the threshold fields for impactionization of each long-channel SOI device at multiple gate voltages,calculating the parameter C in equation (1) of the multiple long-channelSOI devices at multiple gate voltages.

In one embodiment, the method further comprises:

averaging the threshold fields for impact ionization of eachlong-channel SOI device at multiple gate voltages, respectively, andobtaining the initial fitting values of the threshold field F_(I) inequation (1) of each long-channel SOI devices; and/or,

averaging the carrier diffusion lengths in the body region of themultiple long-channel SOI devices at multiple gate voltages, andobtaining the fitting value of the carrier diffusion length L_(b) in thebody region in equation (1); and/or,

taking the average value of the parameter C of the multiple long-channelSOI devices at multiple gate voltages as the initial fitting value ofthe parameter C in equation (1);

substituting the initial fitting value of the parameter C into equation(1), and according to the average value of the carrier diffusion lengthsin the body region of the multiple long-channel SOI devices at multiplegate voltages, determining the threshold fields for impact ionization ofeach SOI device at multiple gate voltages, respectively, as the fittingvalue of the threshold field F_(I) in equation (1) of each long-channelSOI device:

repeating the parameter C extraction steps to obtain the fitting valuesof the parameter C in equation (1) for the multiple long-channel SOIdevices at multiple gate voltages.

In one embodiment, the method further comprises:

extraction of parameter V_(k):

obtaining drain current I_(D) and drain saturation current I_(Dsat) ofmultiple long-channel SOI devices with fixed channel width but variedchannel lengths at multiple gate voltages;

using equation (2) to establish the function with V_(k) as the slope inlong-channel SOI devices;

according to the drain current I_(D) and drain saturation currentI_(Dsat) of the multiple long-channel SOI devices at multiple gatevoltages, and the function with V_(k) as the slope in long-channeldevices, calculating V_(k) of the multiple long-channel SOI devices atmultiple gate voltages; preferably,

the method further comprises:

parameter extraction of carrier diffusion length L_(b) in the bodyregion and C_(k):

using equation (2) to establish the function with

$- \frac{1}{L_{b}}$

as the slope and ln(2C_(k)) as the intercept in long-channel SOIdevices;

calculating the V_(k) average value of each long-channel SOI device atmultiple gate voltages, respectively;

according to the V_(k) average value of each long-channel SOI device atmultiple gate voltages, and the function with

$- \frac{1}{L_{b}}$

as the slope, ln(2C_(k)) as the intercept in long-channel devices,calculating the carrier diffusion lengths L_(b) in the body region andC_(k) of the multiple long-channel SOI devices at multiple gatevoltages.

In one embodiment, the method further comprises:

averaging C_(k) values of the multiple long-channel SOI devices atmultiple gate voltages, and obtaining the fitting value of C_(k) inequation (2); and/or,

averaging the carrier diffusion lengths in the body region of themultiple long-channel SOI devices at multiple gate voltages, andobtaining the fitting value of the carrier diffusion length L_(b) in thebody region in equation (2); and/or,

substituting the average value of parameter C_(k) and L_(b) of themultiple long-channel SOI devices at multiple gate voltages intoequation (2), respectively, and obtaining the V_(k) fitting values inequation (2) of the multiple long-channel SOI devices at multiple gatevoltages.

In another embodiment, the disclosure describes a kink currentcalculation apparatus for SOI device. In this embodiment, the apparatuscomprises: one or more processors; and one or more computer memorydevices arranged to store computer-executable instructions, wherein theone or more processors execute the computer-executable instructions toimplement the kink current calculation method for an SOI device asdescribed above.

In the embodiment of the present application, two factors that affectthe kink current in the SOI device are considered when calculating thekink current of the SOI device, namely, the impact ionization factor andthe parasitic transistor effect factor, so that the calculated kinkcurrent of the SOI device is more accurate without any empiricalparameters introduced, and has a good fitting performance at differentgate voltages for a group of SOI devices of different channel lengths;at the same time, the parameters used in this calculation method areeasy to extract and suitable for circuit simulation.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of theembodiments of the present application, the drawings used in thedescription of the embodiments will be briefly described below. It isobvious that the drawings in the following description are only someembodiments of the present application. Those skilled in the art canalso obtain other drawings based on these drawings without paying anycreative work.

FIG. 1 is a schematic diagram of the kink current of SOI device;

FIG. 2 is a schematic diagram when Jacunski et al. used RPI model forfitting in the background technique;

FIG. 3 is a schematic diagram when the applicant uses RPI model forfitting;

FIG. 4 is a flowchart of the current calculation method of SOI deviceprovided by an embodiment of the application;

FIG. 5 is a schematic diagram of the relationship between F_(I) fittingvalue and the channel length L in experimental example 1 of the presentapplication.

FIG. 6 is a schematic diagram of the relationship between the C fittingvalue and the gate voltage in experimental example 1 of the presentapplication.

FIG. 7 is a schematic diagram for kink current fitting of multiple SOIdevices at multiple gate voltages in experimental example 1 of thepresent application.

FIG. 8 is a schematic diagram for kink current fitting of multiple SOIdevices at multiple gate voltages in experimental example 2 of thepresent application.

FIG. 9 is a schematic diagram for kink current fitting of multiple SOIdevices at multiple gate voltages in experimental example 3 of thepresent application.

FIG. 10 is a schematic diagram of the apparatus structure provided byone embodiment of the present application.

FIG. 11 is a block diagram of the kink current calculation apparatus foran SOI device provided by one embodiment of the present application.

DESCRIPTION OF THE EMBODIMENTS

The technical solutions in the embodiments of the present applicationare clearly and completely described in the following with reference tothe accompanying drawings in the embodiments of the present application.It is obvious that the described embodiments are only some embodimentsof the present application, rather than all embodiments. All otherembodiments obtained by those skilled in the art based on theembodiments of the present application without paying any creative workfall within the scope of protection of the present application.

Referring to FIG. 4, an embodiment of the kink current calculationmethod of an SOI device in this present application is introduced. Inthis embodiment, the method includes the following steps.

S10, Obtaining the impact ionization factor, the parasitic transistoreffect factor, and the drain saturation current of the SOI device,respectively;

When the drain of the SOI device is biased at a large voltage, impactionization in the drain depletion region generates a large number ofelectron-hole pairs. It is enhanced by a parasitic bipolar junctiontransistor, and an additional positive feedback occurs in the bodyregion. Therefore, by adding the impact ionization factor and theparasitic transistor effect factor to the kink current calculation ofthe SOI device, the factors that affect the kink current in the SOIdevice can be better elaborated, making the calculated kink current ofthe SOI device more accurate.

Specifically, one can obtain the channel length and the carrierdiffusion length in the body region of the SOI device, and the parasitictransistor effect factor of the SOI device can be calculated accordingto the channel length and the carrier diffusion length in the bodyregion. The parasitic transistor effect factor of the SOI device has ahyperbolic secant dependence on the channel length and the carrierdiffusion length in the body region of the SOI device.

It should be noted that in the following embodiments: if a P-type SOIdevice is shown, the carrier diffusion length in the body regioncorresponds to the electron diffusion length; accordingly, if an N-typeSOI device is shown, the carrier diffusion length in the body regioncorresponds to the hole diffusion length.

In one embodiment, the parasitic transistor effect factor of the SOIdevice is:

${sech}\left( \frac{L}{L_{b}} \right)$

where L is the channel length of the SOI device and L_(b) is the carrierdiffusion length in the body region of the SOI device.

The impact ionization factor of the SOI device has an exponentialrelationship with the threshold field F_(I) characterizing the impactionization, the depletion region width l_(d), the drain voltage V_(D),and the interpolation function V_(Dse) related to drain saturationvoltage of the SOI device;

In one embodiment, the impact ionization factor is:

${\frac{\left( {V_{D} - V_{Dse}} \right)}{l_{d}}{\exp\left( {- \frac{F_{I}l_{d}}{V_{D} - V_{Dse}}} \right)}};$

Alternatively, the impact ionization factor of the SOI device has anexponential relationship with the drain voltage V_(D), the voltageparameter V_(k) associated with the kink effect, and the interpolationfunction V_(Dse) related to drain saturation voltage of the SOI device;

In one embodiment, the impact ionization factor is:

${\frac{\left( {V_{D} - V_{Dse}} \right)}{V_{k}}{\exp\left( {- \frac{V_{k}}{V_{D} - V_{Dse}}} \right)}}.$

S20, Calculating kink current of the SOI device according to the impactionization factor, the parasitic transistor effect factor, and the drainsaturation current.

In the following, the calculation method of the kink current I_(kink) ofthe SOI device in step S20 will be described through differentembodiments.

Embodiment 1

The calculation method for kink current I_(kink) of the SOI device is:

$\begin{matrix}{{I_{kink} = {C\frac{\left( {V_{D} - V_{Dse}} \right)}{l_{d}}{\exp\left( {- \frac{F_{I}l_{d}}{V_{D} - V_{Dse}}} \right)}{{sech}\left( \frac{L}{L_{b}} \right)}I_{Dsat}}};} & (1)\end{matrix}$

where C is a parameter related to the material and geometry of the SOIdevice, L is the channel length of the SOI device, V_(D) is the drainvoltage of the SOI device, V_(Dse) is the interpolation function relatedto the drain saturation voltage (which links the transition between thelinear and saturation region, and respectively approaches the drainvoltage V_(D) in the linear region and V_(Dsat) in the saturationregion), I_(d) is the depletion region width of the SOI device. F_(I) isthe threshold field for impact ionization of the SOI device, L_(b) isthe carrier diffusion length in the body region of the SOI device,I_(Dsat) is the drain saturation current of the SOI device, and sech (x)is the hyperbolic secant function

$\left( {{\sec\; h\; x} = \frac{2}{e^{x} + e^{- x}}} \right).$

In particular, for long-channel SOI devices, the channel length L ismuch larger than the carrier diffusion length L_(b) in the body region,so:

${{{sech}\left( \frac{L}{L_{b}} \right)} \approx {2{\exp\left( {- \frac{L}{L_{b}}} \right)}}},$

So the above kink current calculation method of SOI device can bechanged as:

${l_{kink} = {2C\frac{\left( {V_{D} - V_{Dse}} \right)}{l_{d}}{\exp\left( {- \frac{F_{I}l_{d}}{V_{D} - V_{Dse}}} \right)}{\exp\left( {- \frac{L}{L_{b}}} \right)}l_{Dsat}}}.$

It can be seen that, in the kink current calculation method of the SOIdevice in the embodiment of the present application, the kink currentand the channel length L of the SOI device can be further approximatedas an exponential dependency, and this kink current calculation methodof the SOI device is all based on physical parameters without anyempirical parameters involved, which is more accurate and reliable.

In one embodiment, the above-mentioned parameter C can be expressed as

$\frac{I_{0}\tau_{b}}{{AE}_{I}n_{i}},$

where I₀ is the reverse saturation current of the SOI device, τ_(b) isthe carrier lifetime in the body region, A is the effectivecross-sectional area of the avalanche zone through which current flows,E_(I) is the threshold energy for impact ionization, and n_(i) is theintrinsic carrier concentration. It should be noted that the expressionof the parameter C here is only an exemplary description, rather than alimitation to the present application. In the subsequent steps offitting the parameter C, it is not necessary to rely on theabove-mentioned I₀, τ_(b), A, E_(I), n_(i) to determine the parameter C.Therefore, in different embodiments, the parameter C is not necessarilysuch an expression, and may have different definitions, which are allwithin the protection scope of the present application.

In one embodiment, the drain saturation current I_(Dsat) of the SOIdevice can be expressed as:

$I_{Dsat} = {\frac{W}{L - l_{d} + {V_{Dse}/E_{sat}}}\mu_{eff}{C_{ox}\left( {V_{GT} - {\frac{1}{2}V_{Dse}}} \right)}V_{Dse}}$

where W is the width of the SOI device, L is the channel length of theSOI device, l_(d) is the width of the depletion region, μ_(eff) is theeffective channel mobility, C_(ox) is the gate oxide capacitance perunit area, V_(Dse) is an interpolation function related to the drainsaturation voltage, which respectively approaches V_(D) in the linearregion and V_(Dsat) in the saturation region, E_(sat) is thecharacteristic field for carrier velocity saturation, and V_(GT) is theeffective gate voltage.

In another embodiment, the drain saturation current I_(Dsat) of the SOIdevice can also be expressed as:

$I_{Dsat} = {\mu_{FET}C_{ox}\frac{{W\left( {V_{GS} - V_{t}} \right)}\alpha_{sat}}{L2}}$

where μ_(FET) is the field effect mobility, C_(ox) is the gate oxidecapacitance per unit area, W is the width of the SOI device, L is thechannel length of the SOI device, V_(GS) is the gate voltage, V_(t) isthe threshold voltage, and α_(sat) is a parameter related to thepinch-off at the drain.

It can be understood that the above only exemplarily gives twocalculation methods of the drain saturation current I_(Dsat) of the SOIdevice, rather than a limitation to this application. In moreembodiments, those skilled in the art can select different drainsaturation current models according to actual usage requirements, andthese transformed embodiments should still fall within the protectionscope of the present application.

In this embodiment, the method also includes the parameter extractionand fitting steps of the threshold field F_(I), the parameter extractionand fitting steps of the carrier diffusion length L_(b) in the bodyregion, and the parameter C extraction and fitting steps. Exemplarily,the above steps are all based on a group of polysilicon thin filmtransistors with the fixed width (W) but varied channel lengths (L).Specifically,

S101, the parameter extraction steps of threshold field F_(I) comprise:

obtaining drain current I_(D) and drain saturation current I_(Dsat) ofmultiple long-channel SOI devices with fixed channel width but variedchannel lengths at multiple gate voltages;

equation (1) is used to establish the function with the threshold fieldF_(I) as the slope in long-channel SOI devices;

according to the drain current I_(D) and drain saturation currentI_(Dsat) of the multiple long-channel SOI devices at multiple gatevoltages, and the function with the threshold field F_(I) as the slopein long-channel devices, the threshold fields for impact ionization ofthe multiple long-channel SOI devices at multiple gate voltages can becalculated.

In one embodiment, for long-channel SOI devices, the channel length L ismuch larger than the carrier diffusion length L_(b) in the body region,so

${{sech}{\left( \frac{L}{L_{b}} \right) = {2{\exp\left( {- \frac{L}{L_{b}}} \right)}}}},$

where I_(kink)=I_(D)−I_(Dsat). Equation (1) can be transformed into

ln

${\left\lbrack \frac{\left( {I_{D} - I_{Dsat}} \right)l_{d}}{I_{Dsat}\left( {V_{D} - V_{Dse}} \right)} \right\rbrack = {{- {F_{I}\left( \frac{l_{d}}{V_{D} - V_{Dse}} \right)}} + {\ln\left( {2C} \right)} - \frac{L}{L_{b}}}};$

Let

${y = \frac{\left( {I_{D} - I_{Dsat}} \right)l_{d}}{I_{Dsat}\left( {V_{D} - V_{Dse}} \right)}},{x = \frac{l_{d}}{V_{D} - V_{Dse}}},$

and the plot ln y˜x can be obtained. F_(I) is the slope, and thethreshold fields for impact ionization of multiple long-channel SOIdevices at multiple gate voltages can be obtained.

S102, the parameter extraction steps of carrier diffusion length L_(b)in the body region comprise:

equation (1) is used to establish the function with

$- \frac{1}{L_{b}}$

as the slope in long-channel SOI devices;

the average value of the threshold fields for impact ionization of eachlong-channel SOI device at multiple gate voltages is calculatedseparately;

according to the average value of the threshold fields for impactionization of each long-channel SOI device at multiple gate voltages,and the function with

$- \frac{1}{L_{b}}$

as the slope in long-channel devices, the carrier diffusion lengths inthe body region of the multiple long-channel SOI devices at multiplegate voltages can be calculated.

In one embodiment, equation (1) can be transformed into

ln

${{{1\left\lbrack \frac{\left( {I_{D} - I_{Dsot}} \right)l_{d}}{I_{Dsot}\left( {V_{D} - V_{Dse}} \right)} \right\rbrack} + F},{\left( \frac{l_{d}}{V_{D} - V_{Dse}} \right) = {{- \frac{L}{L_{b}}} + {\ln\left( {2C} \right)}}}};$

Let

${Y = {{\ln\left\lbrack \frac{\left( {I_{D} - I_{Dsot}} \right)l_{d}}{I_{Dsot}\left( {V_{D} - V_{Dse}} \right)} \right\rbrack} + F}},\left( \frac{l_{d}}{V_{D} - V_{Dse}} \right)$

and the slope of the plot Y˜L is

${- \frac{1}{L_{b}}}.$

With the threshold fields for impact ionization of multiple long-channelSOI devices extracted in step S101 at multiple gate voltages, theiraverage values for an SOI device at different gate voltages can beobtained, and then are substituted into the above equation to obtain thecarrier diffusion lengths in the body region of multiple long-channelSOI devices at multiple gate voltages.

S103, the extraction steps of parameter C comprise:

the average value of carrier diffusion lengths in the body region of themultiple long-channel SOI devices at multiple gate voltages iscalculated;

according to the average value of carrier diffusion lengths in the bodyregion of the multiple long-channel SOI devices at multiple gatevoltages, and the average value of the threshold fields for impactionization of each long-channel SOI device at multiple gate voltages,the parameter C values in equation (1) of the multiple long-channel SOIdevices at multiple gate voltages are calculated.

S104, the threshold fields for impact ionization of each long-channelSOI device at multiple gate voltages are averaged, respectively, and theinitial fitting value of the threshold field F, in equation (1) of eachlong-channel SOI devices is obtained.

S105, the carrier diffusion lengths in the body region of the multiplelong-channel SOI devices at multiple gate voltages are averaged, and thefitting value of the carrier diffusion length L_(b) in the body regionin equation (1) is obtained.

S106, the average value of the parameter C of the multiple long-channelSOI devices at multiple gate voltages is taken as the initial fittingvalue of the parameter C in equation (1);

the initial fitting value of the parameter C is resubstituted intoequation (1), and according to the average value of the carrierdiffusion lengths in the body region of the multiple long-channel SOIdevices at multiple gate voltages, the threshold field for impactionization of each SOI device at multiple gate voltages is determinedseparately, as the fitting value of the threshold field F, in equation(1) of each long-channel SOI device;

the parameter C extraction steps are repeated to obtain the fittingvalues of the parameter C in equation (1) for the multiple long-channelSOI devices at multiple gate voltages.

In this way, the fitting values of the three parameters threshold fieldF_(I), carrier diffusion length L_(b) in body region, and C can beobtained. The fitting value of the threshold field F_(I) has a lineardependence on the channel length L. Based on this, the kink current ofother SOI devices in the same fabrication process can be readilycalculated.

Of course, in more embodiments, the technical solutions of the presentapplication may further include re-substituting the fitting values ofthe three parameters, namely, the threshold field F_(I), the carrierdiffusion length L_(b) in the body region, and C, into the formula (1)and iterating the above steps of parameter extraction and fittingmultiple times to further obtain the fitting values which can achieve asatisfactory fitting performance for three parameters of the thresholdfield F_(I), the carrier diffusion length L_(b) in the body region, andC. Such an embodiment should still be within the concept of the presentapplication.

Two specific experimental examples are provided below to further explainthe kink current calculation method of the SOI device of thisembodiment.

Experimental Example 1

Device type: P-type excimer laser annealed polycrystalline silicon thinfilm transistors.

W/L: 10/25 μm, 10/20 μm, 10/15 μm and 10/10 μm.

Gate voltage: V_(gs)=−3.5,−4,−4.5,−5V.

The fitting values of the threshold field are as follows:

F₁(×10⁵ V/cm) fitting value V_(gs)(V) 10/25 10/20 10/15 10/10 −3.5 2.102.45 2.75 3.00 −4 2.10 2.45 2.75 3.00 −4.5 2.10 2.45 2.75 3.00 −5 2.102.45 2.75 3.00

The fitting value of the carrier diffusion length L_(b) in the bodyregion (Here the carrier diffusion length refers to the electrondiffusion length) is as follows (Since the extracted values of L_(b) atdifferent gate voltages are close, the average value is used as thefitting value):

V_(gs)(V) L_(b) (μm) fitting values −3.5 4.5 −4 4.5 −4.5 4.5 −5 4.5

The fitting values of parameter C are as follows:

C(cm/V) fitting values V_(gs)(V) 10/25 10/20 10/15 10/10 −3.5 0.20 0.200.20 0.20 −4 0.18 0.18 0.18 0.16 −4.5 0.14 0.14 0.16 0.12 −5 0.10 0.100.12 0.10

It can be seen from this experimental example that the same set of Cvalues can be used for SOI devices with different W/Ls. C has a lineardependence on the gate voltage V_(gs), the carrier diffusion lengthL_(b) uses a fixed fitting value, and the threshold field F, is also thesame at different gate voltages. Specifically, the relationship betweenthe threshold field F, and the channel length L is shown in FIG. 5, andthe relationship can be described by a parameter equation,F_(I)=k₁·L+b₁. For the P-type excimer laser annealed polycrystallinesilicon thin film transistors, the parameters are: k₁=−6×10⁷V/cm²,b₁=3.6×10⁵ V/cm; the relationship between C and the gate voltage V_(gs)is shown in FIG. 6, and the relationship can also be described by alinear parameter equation, C=k₂·V_(gs)+b₂. For the P-type excimer laserannealed polycrystalline silicon thin film transistors, the parametersare: k₂=0.068 cm/V², b₂=0.44 cm/V. With reference to FIG. 7 (where thedrain current and the gate voltage are positively correlated, the fouroutput characteristic curves correspond to the gate voltageV_(gs)=−3.5,−4,−4.5,−5V from bottom to top, respectively), it can beseen that in the kink current calculation method of the SOI device ofthe present application, the fitting kink current is highly close to theexperimental data, showing a good fitting performance.

Experimental Example 2

Device type: N-type metal-induced laterally crystallized (MILC)polysilicon thin film transistor (the carrier diffusion length in thebody refers to the hole diffusion length).

W/L: 10/25 μm, 10/20 μm, 10/15 μm and 10/10 μm.

Gate voltage: V_(gs)=11, 12, 13, 14V.

Similarly, referring to FIG. 8 (where the drain current is positivelyrelated to the gate voltage, the four output characteristic curvescorrespond to the gate voltage V_(gs)=11, 12, 13, 14V from bottom totop, respectively), it can be seen that the fitting kink current ishighly close to the experimental data, showing a good fittingperformance.

From the above experimental examples, it can be seen that the kinkcurrent calculation method provided by the present application has agood fitting performance on n- and p-type devices over a wide processrange from low defect density excimer laser annealed (ELA) process tohigh defect density metal induced laterally crystallized (MILC) process.Similarly, there is also a good fitting effect on the partially depletedSOI device with fewer defect states, which will not be repeated here.

Embodiment 2

The calculation method for kink current I_(kink) of the SOI device is:

$\begin{matrix}{I_{kink} = {C_{k}\frac{\left( {V_{D} - V_{Dse}} \right)}{V_{k}}{\exp\left( {- \frac{V_{k}}{V_{D} - V_{Dse}}} \right)}{{sech}\left( \frac{L}{L_{b}} \right)}I_{Dsat}}} & (2)\end{matrix}$

where C_(k) is a parameter related to the material and geometry of theSOI device, L is the channel length of the SOI device, V_(D) is thedrain voltage of the SOI device, V_(Dse) is the interpolation functionrelated to the drain saturation voltage (which links the transitionbetween the linear and saturation region, and respectively approachesthe drain voltage V_(D) in the linear region and V_(Dsat) in thesaturation region), V_(k) is the voltage parameter associated with thekink effect, L_(b) is the carrier diffusion length in the body region ofthe SOI device, I_(Dsat) is the drain saturation current of the SOIdevice, and sech (x) is the hyperbolic secant function

$\left( {{{sech}\; x} = \frac{2}{e^{x} + e^{- x}}} \right).$

In particular, for long-channel SOI devices, the channel length L ismuch larger than the carrier diffusion length L_(b) in the body region,so:

${{sech}{\left( \frac{L}{L_{b}} \right) = {2{\exp\left( {- \frac{L}{L_{b}}} \right)}}}},$

So the above kink current calculation method of SOI device can bechanged as:

$I_{kink} = {2C_{k}\frac{\left( {V_{D} - V_{Dse}} \right)}{V_{k}}{\exp\left( {- \frac{V_{k}}{V_{D} - V_{Dse}}} \right)}{\exp\left( {- \frac{L}{L_{b}}} \right)}{I_{Dsat}.}}$

It can be seen that, in the kink current calculation method of the SOIdevice in the embodiment of the present application, the kink currentand the channel length L of the SOI device can be further approximatedas an exponential dependency, and this kink current calculation methodof the SOI device is all based on physical parameters without anyempirical parameters involved, which is more accurate and reliable.

It should be noted that the selection of the drain saturation current ofthe SOI device can refer to the first embodiment, which will not bedescribed in detail here.

In this embodiment, the method also includes the parameter V_(k)extraction and fitting steps, the parameter extraction and fitting stepsof the carrier diffusion length L_(b) in the body region, and theparameter C extraction and fitting steps. Exemplarily, the above stepsare all based on a group of polysilicon thin film transistors with thefixed width (W) but varied channel lengths (L). Specifically,

S201, the extraction steps of parameter V_(k) comprise:

obtaining drain current I_(D) and drain saturation current I_(Dsat) ofmultiple long-channel SOI devices with fixed channel width but variedchannel lengths at multiple gate voltages;

equation (2) is used to establish the function with V_(k) as the slopein long-channel SOI devices;

according to the drain current I_(D) and drain saturation currentI_(Dsat) of the multiple long-channel SOI devices at multiple gatevoltages, and the function with V_(k) as the slope in long-channeldevices, V_(k) values of the multiple long-channel SOI devices atmultiple gate voltages are calculated.

In one embodiment, for long-channel SOI devices, the channel length L ismuch larger than the carrier diffusion length L_(b) in the body region,so

${{{sech}\left( \frac{L}{L_{b}} \right)} \approx {2{\exp\left( {- \frac{L}{L_{b}}} \right)}}},$

where I_(kink)=I_(D)−I_(Dsat). Equation (2) can be transformed into

${\ln{\left( \frac{I_{D} - I_{Dsat}}{I_{Dsat}} \right) = {{- \frac{V_{k}}{V_{D} - V_{Dse}}} - {L/L_{b}} + {\ln\left( {2C_{k}} \right)}}}};$

Let

${{y = \frac{I_{D} - I_{Dsat}}{I_{Dsat}}},{x = {{- 1}/\left( {V_{D} - V_{Dse}} \right)}}},$

and the plot ln y˜x can be obtained. V_(k) is the slope, and parameterV_(k) of multiple long-channel SOI devices at multiple gate voltages canbe obtained.

It should be noted that, in the deformation of the above formula (2),since

${\ln\left( \frac{V_{D} - V_{Dse}}{V_{k}} \right)}\mspace{14mu}{in}$${\ln\left( \frac{I_{D} - I_{Dsat}}{I_{Dsat}} \right)} = {{\ln\left( \frac{V_{D} - V_{Dse}}{V_{k}} \right)} - \frac{V_{k}}{V_{D} - V_{Dse}} - {L/L_{b}} + {\ln\left( {2C_{k}} \right)}}$

is a logarithmic term, it is a slowly varying term relative to thelinear term

$\frac{V_{k}}{V_{D} - V_{Dse}},$

which can be ignored when extracting the slope.

S202, the parameter extraction steps of carrier diffusion length L_(b)in the body region and C_(k) comprise:

equation (2) is used to establish the function with

$- \frac{1}{L_{b}}$

as the slope and ln(2C_(k)) as the intercept in long-channel SOIdevices:

the V_(k) average value of each long-channel SOI device at multiple gatevoltages is calculated separately;

According to the V_(k) average value of each long-channel SOI device atmultiple gate voltages, and the function with

$- \frac{1}{L_{b}}$

as the slope, ln(2C_(k)) as the intercept in long-channel devices, thecarrier diffusion length L_(b) in the body region and C_(k) of themultiple long-channel SOI devices at multiple gate voltages arecalculated.

In one embodiment, equation (2) can be transformed into

ln

${{\left( \frac{I_{D} - I_{Dsat}}{I_{Dsat}} \right) - {\ln\left( \frac{V_{D} - V_{Dse}}{V_{k}} \right)} + \frac{V_{k}}{V_{D} - V_{Dse}}} = {{{- L}/L_{b}} + {\ln\left( {2C_{k}} \right)}}};$

Let

${Y = {{\ln\left( \frac{I_{D} - I_{Dsot}}{I_{Dsot}} \right)} - {\ln\left( \frac{V_{D} - V_{Dse}}{V_{k}} \right)} + \frac{V_{k}}{V_{D} - V_{Dse}}}},$

and one can obtain that the slope of the plot Y˜L is

$- \frac{1}{L_{b}}$

and the intercept is ln(2C_(k)). With V_(k) values of multiplelong-channel SOI devices extracted in step S201 at multiple gatevoltages, their average value for an SOI device at different gatevoltages can be obtained, and then are substituted into the aboveequation to obtain the carrier diffusion lengths L_(b) in the bodyregion and C_(k) of multiple long-channel SOI devices at multiple gatevoltages.

S203, C_(k) values of the multiple long-channel SOI devices at multiplegate voltages are averaged, and the fitting value of C_(k) in equation(2) is obtained.

S204, the carrier diffusion lengths in the body region of the multiplelong-channel SOI devices at multiple gate voltages are averaged, and thefitting value of the carrier diffusion length L_(b) in the body regionin equation (2) is obtained.

S205, the average of parameter C_(k) and L_(b) of the multiplelong-channel SOI devices at multiple gate voltages are substituted intoequation (2), respectively, and the V_(k) fitting values in equation (2)of the multiple long-channel SOI devices at multiple gate voltages areobtained.

In this way, the fitting values of the three parameters V_(k), carrierdiffusion length L_(b) in body region, and C_(k) can be obtained. TheL_(b) and C_(k) obtained by the fitting are kept constant, and V_(k) hasa certain linear dependence on the channel length L and the gate voltageV_(g). Based on this, the kink current of other SOI devices in the samefabrication process can be readily predicted.

Similar to the first embodiment, in this embodiment, the fitting valuesof the three parameters of V_(k), the carrier diffusion length L_(b) inthe body region, and C_(k) can be further re-substituted into formula(2), and iterate the above steps of parameter extraction and fittingmultiple times to obtain the fitting values which can achieve asatisfactory fitting performance for three parameters of V_(k), thecarrier diffusion length L_(b) in the body region, and C_(k).

A specific experimental example is provided below to further explain thekink current calculation method of the SOI device of this embodiment.

Experimental Example 3

Device type: P-type excimer laser annealed polycrystalline silicon thinfilm transistor (the carrier diffusion length in the body region refersto the electron diffusion length).

W/L: 10/25 μm, 10/20 μm, 10/15 μm and 10/10 μm.

Gate voltage: V_(gs)=−3.5,−4,−4.5,−5V.

The final parameter fitting values are as follows:

L_(b) (μm) C_(k) (×10²) V_(k) (V) fitting values fitting fittingV_(gs)(V) L = 25 L = 20 L = 15 L = 10 value value −3.5 38 42 46 49 6.49.5 −4 38 43 46 50 6.4 9.5 −4.5 39 44 46 52 6.4 9.5 −5 40 45 47 53 6.49.5

It can be seen from this experimental example that L_(b) and C_(k) areboth constants, and V_(k) has a certain linear dependence on the gatevoltage V_(gs) and the channel length L. Specifically, it is expressedby a parameter equation: V_(k)=V_(k0)+a·V_(gs)+b·L. For the P-typeexcimer laser annealed polycrystalline silicon thin film transistors,the parameters are: V_(k0)=52.2V, a=−1.7, b=−8×10³V/cm. With referenceto FIG. 9 (where the drain current and the gate voltage are positivelycorrelated, the four output characteristic curves correspond to the gatevoltage V_(gs)=−3.5,−4,−4.5,−5V from bottom to top, respectively), itcan be seen that in the kink current calculation method of the SOIdevice of the present application, the fitting kink current is highlyclose to the experimental data, showing a good fitting performance.

FIG. 10 is a schematic structural diagram illustrating an electronicdevice, according to an implementation of the present application.Referring to FIG. 10, the electronic device includes a processor, aninternal bus, a network interface, memory, and a non-volatile memory,and certainly can further include other hardware needed by a service atthe hardware level. The processor reads a corresponding computer programfrom the non-volatile memory to the memory for running, and an apparatusfor calculating the kink current of SOI device is logically formed.Certainly, in addition to a software implementation, the presentapplication does not exclude another implementation, for example, alogic device or a combination of hardware and software. That is, anexecution body of the following processing procedure is not limited toeach logical unit, and can also be hardware or a logic device.

Referring to FIG. 11, in the software implementation, the kink currentcalculation apparatus for SOI device comprises an acquiring module 301and a calculating module.

The acquiring module 301 is used to obtain the impact ionization factor,the parasitic transistor effect factor, and the drain saturation currentof the SOI device respectively. The calculating module 302 is used tocalculate the kink current of the SOI device according to the impactionization factor, the parasitic transistor effect factor, and the drainsaturation current.

In the software implementation, the kink current calculation apparatusof the SOI device substantially corresponds to the kink currentcalculation method of the SOI device mentioned in the above embodiments,which will not be described in detail here.

The system, apparatus, module, or unit illustrated in the aforementionedembodiments may be specifically implemented by a computer chip or anentity, or a product having a certain function. A typical implementationdevice is a computer, and the specific form of the computer may be apersonal computer, a laptop computer, a cell phone, a camera phone, asmart phone, a personal digital assistant, a media player, a navigationdevice, an email transmission and reception device, a game console, atablet computer, a wearable device, or a combination of any of thesedevices.

In a typical configuration, a computing device includes one or moreprocessors (CPUs), an input/output interface, a network interface, and amemory.

The memory can include a non-persistent memory, a random access memory(RAM), a nonvolatile memory, and/or another form of memory incomputer-readable media, for example, a read-only memory (ROM) or aflash random access memory (flash RAM). The memory is an example of acomputer-readable medium.

The computer-readable medium includes persistent, non-persistent,movable, and unmovable media that can store information by using anymethod or technology. The information can be a computer-readableinstruction, a data structure, a program module, or other data. Examplesof the computer storage medium include but are not limited to aphase-change random access memory (PRAM), a static random access memory(SRAM), a dynamic random access memory (DRAM), another type of randomaccess memory (RAM), a read-only memory (ROM), an electrically erasableprogrammable read-only memory (EEPROM), a flash memory or another memorytechnology, a compact disc read-only memory (CD-ROM), a digitalversatile disc (DVD) or another optical storage, a magnetic cassette, amagnetic tape, a magnetic disk memory or another magnetic storagedevice, or any other non-transmission medium that can be used to storeinformation accessible to the computing device. Based on the definitionin the present specification, the computer-readable medium does notinclude computer-readable transitory media (transitory media), such as amodulated data signal and carrier.

It is worthwhile to further note that, the terms “include”, “comprise”,or their any other variants are intended to cover a non-exclusiveinclusion, so that a process, a method, a product, or a device thatincludes a list of elements not only includes those elements but alsoincludes other elements that are not expressly listed, or furtherincludes elements inherent to such process, method, product, or device.Without more constraints, an element preceded by “includes a . . . ”does not preclude the existence of additional identical elements in theprocess, method, product, or device that includes the element.

Specific implementations of the present application are described above.Other implementations fall within the scope of the appended claims. Insome situations, the actions or steps described in the claims can beperformed in an order different from the order in the implementationsand the desired results can still be achieved. In addition, the processshown in the accompanying drawings does not necessarily require aparticular execution order to achieve the desired results. In someimplementations, multi-tasking and parallel processing can beadvantageous.

The terms used in the present application are for the purpose ofdescribing particular embodiments only and are not intended to limit thepresent application. The singular forms “a”, “an” and “the” used in thepresent application and the appended claims are also intended to includeplural forms, unless the context clearly indicates otherwise. It shouldalso be understood that the term “and/or” as used herein refers to andencompasses any or all possible combinations of one or more of theassociated listed items.

It should be understood that although various types of information maybe described using terms such as first, second, and third in the presentapplication, such information should not be limited by these terms.These terms are only used to distinguish one type of information fromanother type of information. For example, first information may also bereferred to as second information; similarly, second information mayalso be referred to as first information without departing from thescope of the present application. Depending on the context, the word“if” as used herein may be construed to mean “when . . . ” or “upon . .. ” or “in response to determining”.

The above descriptions are merely some embodiments of the presentapplication, and are not intended to limit the present application. Anyalterations, equivalent substitutions, improvements and the like madewithin the spirit and principle of the present application shall fallwithin the protection scope of the present application.

1. A kink current calculation method for SOI device, comprising:obtaining impact ionization factor, parasitic transistor effect factor,and drain saturation current of the SOI device respectively; calculatingthe kink current of the SOI device according to the impact ionizationfactor, the parasitic transistor effect factor, and the drain saturationcurrent.
 2. The method according to claim 1, wherein obtaining theparasitic transistor effect factor of the SOI device specificallyincludes: obtaining channel length and carrier diffusion length in bodyregion of the SOI device, and calculating the parasitic transistoreffect factor of the SOI device according to the channel length and thecarrier diffusion length in the body region.
 3. The method according toclaim 2, wherein the parasitic transistor effect factor of the SOIdevice has a hyperbolic secant dependence on channel length and carrierdiffusion length in body region of the SOI device.
 4. The methodaccording to claim 1, wherein the impact ionization factor of the SOIdevice has an exponential relationship with threshold field F_(I)characterizing the impact ionization, depletion region width l_(d),drain voltage V_(D), and interpolation function V_(Dse) related to drainsaturation voltage of the SOI device; alternatively, the impactionization factor of the SOI device has an exponential relationship withdrain voltage V_(D), voltage parameter V_(k) associated with kinkeffect, and interpolation function V_(Dse) related to drain saturationvoltage of the SOI device.
 5. The method according to claim 1, whereinthe calculation method for kink current I_(kink) of the SOI device is:$\begin{matrix}{{l_{kink} = {C\frac{\left( {V_{D} - V_{Dse}} \right)}{l_{d}}{\exp\left( {- \frac{F_{I}l_{d}}{V_{D} - V_{Dse}}} \right)}{{sech}\left( \frac{L}{L_{b}} \right)}I_{Dsat}}};} & (1)\end{matrix}$ where C is a parameter related to material and geometry ofthe SOI device, L is channel length of the SOI device, V_(D) is drainvoltage of the SOI device, V_(Dse) is interpolation function related tothe drain saturation voltage, I_(d) is depletion region width of the SOIdevice, F_(I) is threshold field for impact ionization of the SOIdevice, L_(b) is carrier diffusion length in body region of the SOIdevice, and I_(Dsat) is drain saturation current of the SOI device;alternatively, the calculation method for kink current I_(kink) of theSOI device is: $\begin{matrix}{{l_{kink} = {C_{k}\frac{\left( {V_{D} - V_{Dse}} \right)}{V_{k}}{\exp\left( {- \frac{V_{k}}{V_{D} - V_{Dse}}} \right)}{{sech}\left( \frac{L}{L_{b}} \right)}I_{Dsat}}};} & (2)\end{matrix}$ where C_(k) is a parameter related to material andgeometry of the SOI device, L is channel length of the SOI device, V_(D)is drain voltage of the SOI device, V_(Dse) is interpolation functionrelated to the drain saturation voltage, V_(k) is voltage parameterassociated with the kink effect, L_(b) is carrier diffusion length inbody region of the SOI device, and I_(Dsat) is drain saturation currentof the SOI device.
 6. The method according to claim 5, wherein themethod further comprises: parameter extraction of the threshold fieldF_(I): obtaining drain current I_(D) and drain saturation currentI_(Dsat) of multiple long-channel SOI devices with fixed channel widthbut varied channel lengths at multiple gate voltages; using equation (1)to establish function with the threshold field F_(I) as slope inlong-channel SOI devices; according to the drain current I_(D) and drainsaturation current I_(Dsat) of the multiple long-channel SOI devices atmultiple gate voltages, and the function with the threshold field F_(I)as the slope in long-channel devices, calculating the threshold fieldsfor impact ionization of the multiple long-channel SOI devices atmultiple gate voltages.
 7. The method according to claim 6, wherein themethod further comprises: averaging the threshold fields for impactionization of each long-channel SOI device at multiple gate voltages,respectively, and obtaining the initial fitting value of the thresholdfield F_(I) in equation (1) of each long-channel SOI devices.
 8. Themethod according to claim 5, wherein the method further comprises:extraction of the parameter V_(k): obtaining drain current I_(D) anddrain saturation current I_(Dsat) of multiple long-channel SOI deviceswith fixed channel width but varied channel lengths at multiple gatevoltages; using equation (2) to establish the function with V_(k) as theslope in long-channel SOI devices; according to the drain current I_(D)and drain saturation current I_(Dsat) of the multiple long-channel SOIdevices at multiple gate voltages, and the function with V_(k) as theslope in long-channel devices, calculating V_(k) values of the multiplelong-channel SOI devices at multiple gate voltages.
 9. (canceled)
 10. Anelectronic apparatus, comprising: one or more processors; and one ormore computer memory devices arranged to store computer-executableinstructions, wherein the one or more processors execute thecomputer-executable instructions to implement the kink currentcalculation method for an SOI device according to claim
 1. 11. Themethod according to claim 3, wherein the parasitic transistor effectfactor is: ${sech}\left( \frac{L}{L_{b}} \right)$ where L is the channellength of the SOI device and L_(b) is the carrier diffusion length inthe body region of the SOI device.
 12. The method according to claim 4,wherein the impact ionization factor is:${\frac{\left( {V_{D} - V_{Dse}} \right)}{l_{d}}{\exp\left( {- \frac{F_{I}l_{d}}{V_{D} - V_{Dse}}} \right)}};$alternatively, the impact ionization factor is:${\frac{\left( {V_{D} - V_{Dse}} \right)}{V_{k}}{\exp\left( {- \frac{V_{k}}{V_{D} - V_{Dse}}} \right)}}.$13. The method according to claim 6, wherein the method furthercomprises: parameter extraction of the carrier diffusion length L_(b) inthe body region: using equation (1) to establish function with$- \frac{1}{L_{b}}$ as the slope in long-channel SOI devices;calculating average value of the threshold fields for impact ionizationof each long-channel SOI device at multiple gate voltages, respectively;according to the average value of the threshold fields for impactionization of each long-channel SOI device at multiple gate voltages,and the function with $- \frac{1}{L_{b}}$ as the slope in long-channeldevices, calculating the carrier diffusion lengths in the body region ofthe multiple long-channel SOI devices at multiple gate voltages.
 14. Themethod according to claim 13, wherein the method further comprises:averaging the carrier diffusion lengths in the body region of themultiple long-channel SOI devices at multiple gate voltages, andobtaining the fitting value of the carrier diffusion length L_(b) in thebody region in equation (1).
 15. The method according to claim 13,wherein the method further comprises: extraction of the parameter C:calculating average value of carrier diffusion lengths in the bodyregion of the multiple long-channel SOI devices at multiple gatevoltages; according to the average value of carrier diffusion lengths inthe body region of the multiple long-channel SOI devices at multiplegate voltages, and the average value of the threshold fields for impactionization of each long-channel SOI device at multiple gate voltages,calculating the parameter C in equation (1) of the multiple long-channelSOI devices at multiple gate voltages.
 16. The method according to claim15, wherein the method further comprises: taking average value of theparameter C of the multiple long-channel SOI devices at multiple gatevoltages as initial fitting value of the parameter C in equation (1);substituting the initial fitting value of the parameter C into equation(1), and according to average value of the carrier diffusion lengths inthe body region of the multiple long-channel SOI devices at multiplegate voltages, determining the threshold field for impact ionization ofeach SOI device at multiple gate voltages, respectively, as fittingvalue of the threshold field F_(I) in equation (1) of each long-channelSOI device; repeating the parameter C extraction steps to obtain thefitting values of the parameter C in equation (1) for the multiplelong-channel SOI devices at multiple gate voltages.
 17. The methodaccording to claim 8, wherein the method further comprises: parameterextraction of carrier diffusion length L_(b) in the body region andC_(k): using equation (2) to establish function with $- \frac{1}{L_{b}}$as slope and ln(2C_(k)) as intercept in long-channel SOI devices;calculating V_(k) average value of each long-channel SOI device atmultiple gate voltages, respectively; according to the V_(k) averagevalue of each long-channel SOI device at multiple gate voltages, and thefunction with $- \frac{1}{L_{b}}$ as the slope, ln(2C_(k)) as theintercept in long-channel devices, calculating the carrier diffusionlength L_(b) in the body region and C_(k) of the multiple long-channelSOI devices at multiple gate voltages.
 18. The method according to claim17, wherein the method further comprises: averaging C_(k) values of themultiple long-channel SOI devices at multiple gate voltages, andobtaining the fitting value of C_(k) in equation (2); and/or, averagingthe carrier diffusion lengths in the body region of the multiplelong-channel SOI devices at multiple gate voltages, and obtaining thefitting value of the carrier diffusion length L_(b) in the body regionin equation (2); and/or, substituting the average value of parameterC_(k) and the carrier diffusion length L_(b) in the body region of themultiple long-channel SOI devices at multiple gate voltages intoequation (2), respectively, and obtaining the V_(k) fitting values inequation (2) of the multiple long-channel SOI devices at multiple gatevoltages.